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We present a measurement of the branching fraction and fraction of longitudinal polarization of decays, which have two ’s in the final state. We also measure time-dependent violation parameters for decays into longitudinally polarized pairs. This analysis is based on a data sample containing mesons collected with the Belle II detector at the SuperKEKB asymmetric-energy collider in 2019–2022. We obtain , , , and , where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysis to constrain the Cabibbo-Kobayashi-Maskawa angle and obtain two solutions; the result consistent with other Standard Model constraints is . Published by the American Physical Society2025more » « lessFree, publicly-accessible full text available May 1, 2026
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A<sc>bstract</sc> We perform the first search forCPviolation in$$ {D}_{(s)}^{+}\to {K}_S^0{K}^{-}{\pi}^{+}{\pi}^{+} $$ decays. We use a combined data set from the Belle and Belle II experiments, which studye+e−collisions at center-of-mass energies at or near the Υ(4S) resonance. We use 980 fb−1of data from Belle and 428 fb−1of data from Belle II. We measure sixCP-violating asymmetries that are based on triple products and quadruple products of the momenta of final-state particles, and also the particles’ helicity angles. We obtain a precision at the level of 0.5% for$$ {D}^{+}\to {K}_S^0{K}^{-}{\pi}^{+}{\pi}^{+} $$ decays, and better than 0.3% for$$ {D}_s^{+}\to {K}_S^0{K}^{-}{\pi}^{+}{\pi}^{+} $$ decays. No evidence ofCPviolation is found. Our results for the triple-product asymmetries are the most precise to date for singly-Cabibbo-suppressedD+decays. Our results for the other asymmetries are the first such measurements performed for charm decays.more » « lessFree, publicly-accessible full text available April 1, 2026
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A<sc>bstract</sc> Using data samples of 983.0 fb−1and 427.9 fb−1accumulated with the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energye+e−colliders, singly Cabibbo-suppressed decays$$ {\Xi}_c^{+}\to p{K}_S^0 $$ ,$$ {\Xi}_c^{+}\to \Lambda {\pi}^{+} $$ , and$$ {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} $$ are observed for the first time. The ratios of branching fractions of$$ {\Xi}_c^{+}\to p{K}_S^0 $$ ,$$ {\Xi}_c^{+}\to \Lambda {\pi}^{+} $$ , and$$ {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} $$ relative to that of$$ {\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+} $$ are measured to be$$ {\displaystyle \begin{array}{c}\frac{\mathcal{B}\left({\Xi}_c^{+}\to p{K}_S^0\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(2.47\pm 0.16\pm 0.07\right)\%,\\ {}\frac{\mathcal{B}\left({\Xi}_c^{+}\to \Lambda {\pi}^{+}\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(1.56\pm 0.14\pm 0.09\right)\%,\\ {}\frac{\mathcal{B}\left({\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+}\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(4.13\pm 0.26\pm 0.22\right)\%.\end{array}} $$ Multiplying these values by the branching fraction of the normalization channel,$$ \mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)=\left(2.9\pm 1.3\right)\% $$ , the absolute branching fractions are determined to be$$ {\displaystyle \begin{array}{c}\mathcal{B}\left({\Xi}_c^{+}\to p{K}_S^0\right)=\left(7.16\pm 0.46\pm 0.20\pm 3.21\right)\times {10}^{-4},\\ {}\mathcal{B}\left({\Xi}_c^{+}\to \Lambda {\pi}^{+}\right)=\left(4.52\pm 0.41\pm 0.26\pm 2.03\right)\times {10}^{-4},\\ {}\mathcal{B}\left({\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+}\right)=\left(1.20\pm 0.08\pm 0.07\pm 0.54\right)\times {10}^{-3}.\end{array}} $$ The first and second uncertainties above are statistical and systematic, respectively, while the third ones arise from the uncertainty in$$ \mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right) $$ .more » « lessFree, publicly-accessible full text available March 1, 2026
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We measure the branching fraction and -violating flavor-dependent rate asymmetry of decays reconstructed using the Belle II detector in an electron-positron collision sample containing mesons. Using an optimized event selection, we find signal decays in a fit to background-discriminating and flavor-sensitive distributions. The resulting branching fraction is and the -violating asymmetry is . Published by the American Physical Society2025more » « lessFree, publicly-accessible full text available April 1, 2026
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A<sc>bstract</sc> We report measurements of the absolute branching fractions$$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)$$,$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)$$, and$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{\pm }X\right)$$, where the latter is measured for the first time. The results are based on a 121.4 fb−1data sample collected at the Υ(10860) resonance by the Belle detector at the KEKB asymmetric-energye+e−collider. We reconstruct one$${B}_{s}^{0}$$meson in$${e}^{+}{e}^{-}\to \Upsilon\left(10860\right)\to {B}_{s}^{*}{\overline{B} }_{s}^{*}$$events and measure yields of$${D}_{s}^{+}$$,D0, andD+mesons in the rest of the event. We obtain$$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)=\left(68.6\pm 7.2\pm 4.0\right)\%$$,$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)=\left(21.5\pm 6.1\pm 1.8\right)\%$$, and$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{\pm }X\right)=\left(12.6\pm 4.6\pm 1.3\right)\%$$, where the first uncertainty is statistical and the second is systematic. Averaging with previous Belle measurements gives$$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)=\left(63.4\pm 4.5\pm 2.2\right)\%$$and$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)=\left(23.9\pm 4.1\pm 1.8\right)\%$$. For the$${B}_{s}^{0}$$production fraction at the Υ(10860), we find$${f}_{s}=\left({21.4}_{-1.7}^{+1.5}\right)\%$$.more » « lessFree, publicly-accessible full text available April 1, 2026
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We measure the branching fraction of the decay using data collected with the Belle II detector at the SuperKEKB collider. The data contain meson pairs produced in energy-asymmetric collisions at the resonance. The measured branching fraction , where the first uncertainty is statistical and the second is systematic, is more precise than previous results and constitutes the first observation of the decay with a significance of 6.5 standard deviations. Published by the American Physical Society2025more » « lessFree, publicly-accessible full text available February 1, 2026
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We measure the time-integrated asymmetry in decays reconstructed in events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and , respectively. The decays are required to originate from the decay, which determines the charm flavor at production time. A control sample of decays is used to correct for production and detection asymmetries. The result, , is consistent with previous determinations and with symmetry. Published by the American Physical Society2025more » « lessFree, publicly-accessible full text available January 1, 2026
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We report a measurement of the cross section in the energy range from 0.62 to 3.50 GeV using an initial-state radiation technique. We use an data sample corresponding to of integrated luminosity, collected at a center-of-mass energy at or near the resonance with the Belle II detector at the SuperKEKB collider. Signal yields are extracted by fitting the two-photon mass distribution in events, which involve a decay and an energetic photon radiated from the initial state. Signal efficiency corrections with an accuracy of 1.6% are obtained from several control data samples. The uncertainty on the cross section at the and resonances is dominated by the systematic uncertainty of 2.2%. The resulting cross sections in the 0.62–1.80 GeV energy range yield for the leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. This result differs by 2.5 standard deviations from the most precise current determination. Published by the American Physical Society2024more » « lessFree, publicly-accessible full text available December 1, 2025
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Abstract A series of data samples was collected with the Belle II detector at the SuperKEKB collider from March 2019 to June 2022. We determine the integrated luminosities of these data samples using three distinct methodologies involving Bhabha (), digamma (), and dimuon () events. The total integrated luminosity obtained with Bhabha, digamma, and dimuon events is (426.88 ± 0.03 ± 2.61) fb−1, (429.28 ± 0.03 ± 2.62) fb−1, and (423.99 ± 0.04 ± 3.83) fb−1, where the first uncertainties are statistical and the second are systematic. The resulting total integrated luminosity obtained from the combination of the three methods is (427.87 ± 2.01) fb−1.more » « lessFree, publicly-accessible full text available January 1, 2026
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We present a measurement of the branching fraction and time-dependent charge-parity ( ) decay-rate asymmetries in decays. The data sample was collected with the Belle II detector at the SuperKEKB asymmetric collider in 2019–2022 and contains meson pairs from decays. We reconstruct signal decays and fit the parameters from the distribution of the proper-decay-time difference of the two mesons. We measure the branching fraction to be and the direct and mixing-induced asymmetries to be and , respectively, where the first uncertainties are statistical and the second are systematic. We observe mixing-induced violation with a significance of 5.0 standard deviations for the first time in this mode. Published by the American Physical Society2025more » « lessFree, publicly-accessible full text available January 1, 2026